ACTH AND PHORBOL ESTER-STIMULATED REDISTRIBUTION OF PROTEIN-KINASE-C IN HUMAN CORTISOL-PRODUCING ADRENAL ADENOMA

We studied the steroidogenetic action and concomitant subcellular redistribution of protein kinase C (PKC) in cortisol hypersecreting adrenal adenoma cells obtained from two patients with Cushing's syndrome. Isolated adenoma cells were treated with 10(-9) M and 10(-6) M 12-O-tetradecanoyl phorbol-13-acetate (TPA) or 10(-6) M ACTH. Treatment of the isolated adenoma cells with TPA resulted in cortisol secretion equivalent to that with ACTH-treatment. Immunoblot analysis of PKC during treatment with ACTH or TPA showed that PKCbeta translocated from cytosol to membrane. A small amount of PKCalpha, but not membrane-associated PKCalpha, was detectable in the cytosolic fraction. It appeared that TPA-induced cortisol secretion mimicked ACTH-induced cortisol secretion, and that PKCbeta translocated from cytosol to membrane on stimulation by both ACTH and TPA. We suggested that ACTH-induced cortisol secretion in human cortisol hypersecreting adrenal adenoma is mediated by PKCbeta activation.